Quote Originally Posted by Nakamura
Just to add to what Gator said ... keeping more than a couple of buy-ins at a Poker site is just plain dumb. As a poker player you should have enough discipline to take this money and put it into a bank account where it earns interest! Poker sites, like insurance companies, make serious money from pool of money they are free to invest.
Combining Nakamura's post above w/ Gator's I'd suggest taking whatever you are willing to lose, call that your bankroll, keep it in a separate bank account you won't touch except for poker. You can earn interest on it and yet still be properly rolled to play 5nl. You can track your play and wait until you are properly rolled for 10nl to move up (or move down to 2nl if you start losing and your bankroll drops). This way you don't fall into the trap of playing beyond your skill level and keep losing money just because you can afford to do it. I'd want more than a couple of buy-ins on my poker site of choice though. I've had 4+ buy-in downswings in one day.